Tandem propeller assembly for a marine propulsion unit

Abstract

A tandem propeller assembly for use with a marine propulsion unit is disclosed wherein a single shock-absorber assembly is utilized to assure damping effects for both propellers so as to protect the propulsion system from being damaged when either propeller is obstructed by drifting wood or other debris. Each of the preferred embodiments disclosed provides a simple structure for absorbing impacts upon either propeller in a tandem propeller assembly while minimizing any increase in the surface area of contact with the water which would increase the propulsion resistance and would result in speed loss.

We claim: 
     
       1. A tandem propeller assembly for use in a marine propulsion unit including a drive shaft, comprising: a first propeller unit;   a second propeller unit located in tandem relative to the first propeller unit;   corotation connector means for positively drivingly connecting the first and second propeller units together for corotation in the same direction;   a single shock absorber; and   drive connecting means for drivingly interconnecting at least one of the propeller units to a drive shaft through said single shock absorber such that said single shock absorber protects the marine propulsion unit from damage in the event that either of the propeller units is obstructed by debris during operation.   
     
     
       2. A tandem propeller assembly as claimed in claim 1, wherein said corotating connector means comprises a spline connection between said propeller units. 
     
     
       3. A tandem propeller assembly as claimed in claim 1 or 2, wherein said shock absorber is an elastic member. 
     
     
       4. A tandem propeller assembly as claimed in claim 1 or 2, wherein said drive connecting means comprises at least an inner collar adapted to engage a drive shaft in driving relationship and an inner cylinder drivingly connected to at least one propeller unit, and wherein said shock absorber is connected between said inner collar and inner cylinder so as to transmit rotary motion between said inner collar and inner cylinder. 
     
     
       5. A tandem propeller assembly as claimed in claim 4, wherein said inner collar and inner cylinder are concentrically arranged, and said shock absorber comprises an elastic member sandwiched between and engaging in driving relationship said inner collar and inner cylinder. 
     
     
       6. A tandem propeller assembly as claimed in claim 5, wherein said inner cylinder is directly connected only to one propulsion unit. 
     
     
       7. A tandem propeller assembly as claimed in claim 1, wherein said drive connecting means is arranged to directly drivingly connect only one propeller unit to a drive shaft. 
     
     
       8. A tandem propeller assembly as claimed in claim 7, said drive connecting means including an inner collar adapted to be drivingly connected to a drive shaft and said first propeller unit comprising a first inner cylinder; said inner collar disposed concentrically with said first inner cylinder;   said shock absorber comprising an elastic member sandwiched between said inner collar and said first inner cylinder, and said elastic member connecting in driving relationship said inner collar and first inner cylinder.   
     
     
       9. A tandem propeller assembly as claimed in claim 8, wherein said corotation connector means includes a spline connector arrangement. 
     
     
       10. A tandem propeller assembly as claimed in claim 8, wherein said second propeller unit comprises a second inner cylinder; and wherein said corotation connector means comprises a corotation connector between said first and second inner cylinders.   
     
     
       11. A tandem propeller assembly as claimed in claim 8, wherein said first and second propeller units respectively comprise first and second outer cylinders, and wherein said corotation connector means comprises a corotation connector between said first and second outer cylinders. 
     
     
       12. A tandem propeller assembly as claimed in claim 10 or 11, wherein said corotation connector comprises radially and axially extending interconnected spline elements. 
     
     
       13. A tandem propeller assembly as claimed in claim 1, said first and second propeller units respectively comprising first and second inner cylinders; said drive connecting means comprising an inner collar adapted to engage a drive shaft in driving relationship and an inner intermediate cylinder;   said shock absorber connecting said inner collar and said inner intermediate cylinder together so as to transmit rotary motion between said inner collar and said inner intermediate cylinder;   said corotation connector means comprising corotation connectors connecting said inner intermediate cylinder and said first and second inner cylinders of said propeller units in driving relationship.   
     
     
       14. A tandem propeller assembly as claimed in claim 13, wherein said inner intermediate cylinder is concentric with said inner collar and said shock absorber comprises an elastic member sandwiched between said inner collar and said inner intermediate cylinder so as to transmit rotary motion between said inner collar and inner intermediate cylinder. 
     
     
       15. A tandem propeller assembly as claimed in claim 13 or 14, wherein said corotation connectors comprise radially and axially extending interconnected spline elements. 
     
     
       16. A tandem propeller assembly for use in a marine propulsion units comprising: a drive shaft;   a first propeller unit;   a second propeller unit;   a single shock absorber arranged between said drive shaft and each of said propeller units; and   drive connecting means for drivingly connecting said first and second propeller units to said drive shaft for rotation in the same direction through said single shock absorber such that said single shock absorber protects the marine propulsion unit from damage in the event that either of the first and second propeller units is obstructed by debris during operation.   
     
     
       17. A tandem propeller assembly as claimed in claim 16, wherein said shock absorber comprises an elastic member secured between said drive shaft and at least one of said propeller units. 
     
     
       18. A tandem propeller assembly as claimed in claim 16 or 17, wherein said shock absorber is secured only between said drive connecting means and one of said propeller units, and the other of said propeller units is driven by said drive shaft through said one propeller unit. 
     
     
       19. A tandem propeller assembly as claimed in claim 18, wherein said shock absorber drivingly and resiliently connects the drive shaft to said one propeller unit. 
     
     
       20. A tandem propeller assembly as claimed in claim 17, wherein said at least one propeller unit comprises an outer collar including an outer cylinder and an inner cylinder drivingly connected to the outer cylinder, and radially spaced from said outer cylinder; said drive connecting means including an inner collar member radially spaced from the inner cylinder and which is driven by said drive shaft; and   wherein said elastic member is sandwiched between said inner collar and said inner cylinder in driving relationship.   
     
     
       21. A tandem propeller assembly as claimed in claim 20, wherein said elastic member is fuse bonded to said inner collar and said inner cylinder. 
     
     
       22. A tandem propeller assembly as claimed in claim 20, wherein in said elastic member is secured only between said drive connecting means and one of said propeller units; wherein the other propeller unit also includes an outer collar including an other outer cylinder drivingly connected to an other inner cylinder radially spaced from said other outer cylinder of said other propeller unit, and the other inner cylinder of said other propeller unit being drivingly connected to the drive shaft via said inner cylinder of said one propeller unit.   
     
     
       23. A tandem propeller assembly as claimed in claim 20, wherein the other propeller unit also includes an outer collar and an inner cylinder, and the outer collars of said propeller units are drivingly interconnected. 
     
     
       24. A tandem propeller assembly as claimed in claim 16, including corotation connector means for positively connecting together said propeller units for corotation. 
     
     
       25. A tandem propeller assembly as claimed in claim 16, wherein said drive connecting means is arranged to drivingly connect only one of said first and second propeller units to the drive shaft, and corotation connector means for positively connecting together said propeller units for corotation. 
     
     
       26. A tandem propeller assembly as claimed in claim 21, each of said propeller units including concentric outer and inner cylinders drivingly connected together, said corotation connector means connecting said inner cylinders together. 
     
     
       27. A tandem propeller assembly as claimed in claim 21, each of said propeller units including concentric outer and inner cylinders drivingly connected together, said corotation connector means connecting said outer cylinders together. 
     
     
       28. A tandem propeller assembly as claimed in claims 24, 25, 26 or 27, said corotation connector means comprising radially and axially extending interconnected spline elements. 
     
     
       29. A tandem propeller assembly as claimed in claim 24, each of said propeller units including concentric outer and inner cylinders drivingly connected together; said drive connecting means including an inner intermediate cylinder;   said corotation connector means connecting together said inner intermediate cylinder and said inner cylinders of said propulsion units;   said shock absorber disposed between said drive shaft and said inner intermediate cylinder.   
     
     
       30. A tandem propeller assembly as claimed in claim 29, wherein said corotation connector means comprises axially and radially extending interconnected spline elements.